and life cycle—Verticillium wilt
The fungus that causes Verticillium wilt can survive for years in the soil. It enters the tree through
young roots, establishing itself in the water-conducting tissues of the plant, and renders the xylem vessels
no longer functional. Cool spring weather is most favorable for disease development. High summer temperatures
actually kill the fungus in the tree. If new infection through the roots does not occur, trees recover
and grow normally the next year. Although the pathogen may reside in roots for a period of time, old infections
eventually die. Once roots have penetrated below the level of inoculum in the soil, new infections will
not occur and symptoms will virtually disappear.